Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
  • C03B5/16—Special features of the melting process; Auxiliary means specially adapted for glass-melting furnaces
  • C03B5/26—Outlets, e.g. drains, siphons; Overflows, e.g. for supplying the float tank, tweels
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
  • C03B37/08—Bushings, e.g. construction, bushing reinforcement means; Spinnerettes; Nozzles; Nozzle plates
  • C03B37/09—Bushings, e.g. construction, bushing reinforcement means; Spinnerettes; Nozzles; Nozzle plates electrically heated
  • C03B37/092—Direct-resistance heating
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
  • C03B5/02—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture in electric furnaces, e.g. by dielectric heating
  • C03B5/027—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture in electric furnaces, e.g. by dielectric heating by passing an electric current between electrodes immersed in the glass bath, i.e. by direct resistance heating
  • C03B5/0275—Shaft furnaces
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
  • C03B5/16—Special features of the melting process; Auxiliary means specially adapted for glass-melting furnaces
  • C03B5/18—Stirring devices; Homogenisation
  • C03B5/183—Stirring devices; Homogenisation using thermal means, e.g. for creating convection currents
  • C03B5/185—Electric means
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B7/00—Distributors for the molten glass; Means for taking-off charges of molten glass; Producing the gob, e.g. controlling the gob shape, weight or delivery tact
  • C03B7/08—Feeder spouts, e.g. gob feeders
  • C03B7/094—Means for heating, cooling or insulation
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P40/00—Technologies relating to the processing of minerals
  • Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping
  • Y02P40/57—Improving the yield, e-g- reduction of reject rates

Definitions

• This invention relates to the production of molten material and, more particularly, to a vertical melter for the making of molten glass by electric melting techni ques.
• the glass undergoes the stages of being prepared by melting batch materials, which float on the molten glass at one end of the furnace, fining the molten glass in a succeeding zone, which in certain cases may be isolated from the first zone by a wall, and conditioning, quieting and cooling the molten glass to a temperature suitable for manufacture into glass products in a conditioning or working zone, which may also be substantially isolated.
• These furnaces may be gas fired or electric melt furnaces.
• a common system for producing glass filaments or fibers includes a furnace having forehearths extending therefrom through which molten glass in the furnace is carried to a plurality of spaced, apart bushings or other devices, such as spinners, located along the bottom wall of the forehearths.
• the forehearths can extend directly from the furnace or can extend as branches from one or more main channels carrying the molten glass from the furnace.
• the glass from each forehearth flows through openings by gravity into the bushings therebelow with molten glass streams from the bushings or spinners being formed into glass filaments or fibers.
• Vertical melters which permit glass to be formed directly from a furnace or melting region.
• one type of arrangement uses a strip or screen of platinum or platinum alloy disposed in the furnace region.
• the platinum typically is perforated or slotted to facilitate circulation of molten glass.
• Electric current is passed through the strip or screen to melt the raw batch by resistive heating of the screen.
• a forming means such as a bushing, is connected directly to the melter to provide streams of molten glass that are formed into fibers by various means.
• the melter is a shallow vertical melter that supplies molten material of uniform temperature to one or more product forming outlets located at the bottom of the melter. During operation, the melter establishes within the molten material of the melter a horizontal heating zone of substantially uniform temperature condition throughout.
• molten glass in the melter rises to the molten glass/raw batch interface as a result of thermal currents caused by the heating zone.
• Molten glass moves across the upper surface of the molten body where it can easily degas.
• the thermal currents effect mixing and fining of the glass in such a way to promote uniform temperature of the molten glass in horizontal layers throughout the molten body.
• the result is a supply of glass of desired uniform temperature delivered at the entrance to the melter outlets.
• the zone of the uniformly heated material is established in preferred form by operation of joule effect electrodes arranged according to the invention in generally opposed spaced apart relationship.
• the electrodes a re disposed in two groups, each in generally horizontal and laterally spaced apart relationship; the electrodes in each group are also arranged in opposed space apart relation.
• Means for supplying electrical current to the electrodes matches electrical current in each electrode with the particular spaced apart relationship of the electrodes to form the heating zone of substantially uniform temperature and thereby mix and move the molten glass to supply glass of uniform temperature to the entrance outlets of the melter.
• Figure 1 is a plane elevational view of a glass melting furnace and fiber forming apparatus utilizing the present invention.
• Figure 2 illustrates a schematic of one embodiment of this invention using equalized current flow through the individual electrodes.
• Figure 3 is a vertical sectional view, with parts shown in elevation, similar to Figure 1, but illustrating a different form of the present invention capable of carrying out the method of the present invention.
• Figure 4 is a vertical sectional view, with parts shown in elevation, similar to Figures 1 and 2, but illustrating a third form of the present invention capable of carrying out the method of the present invention.
• Figure 5 is a vertical sectional view taken along the plane 5-5 of Figure 4.
• Figure 6 is an enlarged sectional view, with parts shown in elevation, taken along the plane 6-6 of Figure 5.
• Figure 7 is a diagram showing the temperature relationship of temperature determinations taken along a medial vertical axis of a furnace constructed in accordance with Figure 3.
• Figure 8 is a diagram similar to Figure 7 but utilizing different operating conditions.
• Figure 9 is a diagrammatic representation of the location at which various thermocouple temperature determinations were made in a furnace constructed in accordance with Figure 3.
• FIG 10 is a diagram in which the temperature determinations made in accordance with Figure 9 are plotted against the thermocouple locations of Figure 9.
• Figure 11 is a diagram similar to Figure 10 but wherein the operating conditions were varied.
• the melter is made of refractory 10 and hol ⁇ s a body of molten glass 11 covered by a blanket 12 of pulverant raw glass batch material.
• the raw batch material may be for wool glass, textile glass, bottle glass, flat glass, or basalt or the like.
• Extending through side walls 13 and 14 is at least one pair of opposed, movable electrodes 15 ana 16.
• the sides and bottom of the melter are made from a suitdble refractory material which can withstand the high temperature attendant with the melting of glass.
• the individual electrodes 15 and 16 a re molybdenum. It should be understood that the embodiment of Figure 1 is not limited to tne use of two electrodes and that any number of electrodes greater than two may be used.
• the spaced apart opposed electrodes located within the vessel and the means for controllably supplying electrical current to each of the opposed electrodes cause electrical current to flow between them through the molten material to cause heating thereof by joule effect.
• the placement of the electrodes relative to each other and the interior surfaces of the melter, and the means for controllably supplying electrical current to each electrode is effective during formation of an isothermal heating zone. This zone promotes essentially isothermal conditions across given horizontal planes of the body of molten material and effects molten glass of uniform temperature at the exit openings of the melter.
• Any type of forming apparatus may be employed with melter 11 such as a bottle machine or spinner for producing insulation. Shown is a textile type fiber forming bushing 20 mounted in the bottom of melter 10. Glass fibers 22 may be pulled by a winder or other suitable mechanism not illustrated. The fibers 22 are gathered into a strand by a gathering shoe 24.
• the fiber forming bushing 20 may be a foraminous plate having a plurality of apertures which are sized to draw glass fibers of the desired denier.
• the combination of heating produced by joule effect in the vicinity of the interface of the individual electrodes 15 and 16 within the molten glass 11 produces the isothermal conditions within the vessel to permit the fibers to be drawn without requiring further processing to produce temperatures which permit glass fiber drawing.
• One arrangement that can be employed to achieve melting and glass delivery according to the invention uses the dimension between opposed electrode tips.
• This dimension is generally in the range of two inches to eighteen inches, and preferably three to twelve inches. More preferably, this dimension is four to eight inches. While the temperature in a given zone or plane may vary somewhat, we generally found the temperature of a given plane to vary no more than 10°C (50° F), preferably no more than -3.9°C (25o F).
• the dimensions between electrodes and between electrodes and forming means establish a circulation pattern above the electrodes with the coolest molten glass in the melter, i.e., the molten glass near the floor, flowing to the forming means.
• the electrodes closest to the floor of the melter are 50.8 to 304.8 millimeters (2 to 12 inches) from the floor.
• this distance is 50.8 to 152.4 millimeters (2 to 6 inches) from the floor.
• Electrodes need not pass through the side walls of furnace 10, but instead may enter the molten glass from above its top surface. Accordingly, a portion of each electrode is submerged in molten glass 11, and a portion of each electrode is exposed to the environment adjacent the raw batch/molten glass interface. Means must be located at this interface for preventing oxidation of the electrode. Typically, a cooling means such as a cooling jacket with circulating nitrogen or water provides the needed protection.
• a cooling means such as a cooling jacket with circulating nitrogen or water provides the needed protection.
• top-entering electrodes will be constructed in a knee/ankle configuration employing two elbows so that the portion of electrodes 16 submerged below molten glass 11 where penetration into the center of furnace 10 from the side walls still can be varied. This is the preferred design when a high resistivity glass and a low resistivity refractory a re employee. Thus, pairs of electrodes 16 can still be moved towards or away from each other depending on furnace conditions.
• Figure 2 illustrates a schematic of another embodiment of the present invention which uses the combination of two arrays of electrodes disposed within the glass to heat molten glass to a sufficiently uniform temperature to permit glass fibers to be drawn directly from the bottom of the furnace through a textile type bushing.
• FIG 2 also illustrates an electrical schematic of the power supply 30 illustrated in Figure 1.
• the power supply 30 includes a resistance heating power supply 44 which is comprised of a transformer 46 having secondary terminals 47 and 48 which are respectively coupled to the center taps 50 and 52 of first and second arrays of inductors 54 and 56 and to equalize the current flowing to individual electrodes 60.
• the ends 64 and 66 of each of the first array of center tapped inductors 54 are coupled to a different individual electrode 60 within array 68 so that each electrode is coupled to only a single end of one of the inductors within the array.
• each of second array of center tapped inductors 56 are coupled to a different individual electrode 60 within array 74 so that each electrode is coupled to only a single end of one of the inductors within the array.
• a silicon controlled rectifier (SCR) 42 is provided in the input to transformer 46 of the resistance heating power supply 44 to permit control of the amount of current being drawn by electrodes 60 for resistance heating within the arrays 68 and 74 by adjusting the firing current of the SCR. It should be understood that the number of electrodes 60 and associated current splitting inductors 54 and 56 illustrated were chosen for purposes of illustration and does not signify the limitation of the invention.
• Figure 2 also demonstrates that multiple bushings may be utilized on a single melter. Multiple openings 80 in the floor for discharge of molten material are shown as are additional electrodes 60 in arrays 6b and 74.
• the electrode power supply circuits of Figure 2 each equalize the flow of current through the individual electrodes disposed within the molten glass.
• the equalization of the flow of current in each electrode within the glass is produced by applying electrical power for driving either the electrodes directly or indirectly through additional cascaded current splitting inductors through the center tap of an inductor having ends which are respectively coupled either directly to electrodes or to the center taps of the additional cascaded current splitting inductors.
• the magnetic flux in the half of the inductor between the center tap and the point of the connection having increased current flow increases which induces an opposing EMF in the inductor in accordance with Lenz's law of magentic induction.
• This induced EMF opposes the increase in the current flowing in the electrode having the increased flow and causes an increase of current flow in the other half of the inductor which tends to equalize the current flowing in both circuits coupled to the ends of the inductor.
• the current splitting inductor equalizes the flow of current in each of the arrays.
• the current splitting inductors must be configured such that the ampere turns on each side of the center tap a r e not equal but are such that the electrodes in the array have the flow of current equalized.
• the embodiment of the furnace 100 includes side walls 102 and end walls (not shown) positioned above a bottom wall 104 and cooperating therewith to confine a body of molten glass 101.
• the end walls (not shown) were lined with an erosion-resistant chromic oxide refractory which was water-cooled to increase its electrical resistivity. The minimal cooling of the end walls did not materially affect the heat flow pattern within the molten glass in the furnace of Figure 3.
• the bottom wall 104 is provided with a discharge opening 105 located centrally thereof for conveying glass from the molten body 101 to a lower glass fiber-forming bushing 110. Interposed between the bottom wall 104 and the bushing 110 a re a pair of bushing blocks 106 and 108 having apertures registering with the discharge opening 105 of the bottom wall 104.
• Electrodes 112 Projecting through the side walls 1 02 a re e l ect r i c a l l y e n e rg i z a b l e e l ect r od e s 1 1 2 s imilar to the electrodes 15, 16 and 60 of the previously-described embodiments of Figures 1 and 2 and energtzed by power means similar to that illustrated in Figure 2 of the drawings.
• the electrodes 112 are immersed in the body 101 of molten glass intermediate the bottom wall 104 and a layer of blanket of particulate, solid glass batch 112 superimposed on the molten body 101.
• the molten glass in the body or pool 101 is heated, primarily at the inner ends or “tips" of the electrodes and in the space intermediate the electrodes, so that the heated glass is thermally circulated upwardly from the electrode tips, indicated generally by the directional arrows 115.
• the upwardly flowing heated molten glass flows to and across the undersurface of the batch blanket 114 to melt the batch blanket as hereinbefore explained.
• the molten glass thus flows upwardly from the electrode tips generally horizontally and outwardly along the undersurface of the batch blanket to carry o ⁇ t this melting function.
• the heated molten glass primarily returns to the electrode tips for reheating and reci rcul ati on, the glass generally flowing downwardly along the side walls 102 and confined by the end walls (not shown). This recirculation to the electrode tips is indicated by the directional arrows bearing the reference numerals 116. A minor portion of the circulating heated glass flows downwardly past the electrodes 112 to that portion of the body or pool 101 of molten glass beneath the electrodes for eventual flow downwardly through the outlet passage 105 in the bottom wall 104, the central apertures of the bushing blocks 106, 108, and then into the bushing 110 for processing therein into glass fibers.
• the molten glass In the manufacture of glass products, including the manufacture of fiberglass products, the molten glass inevitably contains "seeds" or minute gas bubbles entrapped within the molten glass and carried into the final product. Generally, such seeds a re removed by "fining" the glass, i.e., by holding the glass in a virtually stagnant or slowly moving pool for an extended period of time until the seeds are removed by this upward travel through the glass body to the surface of the body.
• the "seed count" of the molten glass is determined by counting the number of seeds per cubic meter (inch) of glass. Seed counts on the order of 16E-04 (100) are fairly common where bubblers are not used in the melting process. Where bubblers are used, initial seed counts on the order of 197E-04 to 246E-04 (1200 to 1500) are not unusual.
• low seed counts a re obtained.
• seed counts ranging from 0 to 9E-04 (0 to 52) seeds per cubic meter (inch) were obtained, and a n average seed count of 5E-04 (28) per cubic meter (inch) resulted over an extended period of operation.
• This low seed count apparently results from the mobility of the hottest glass at ana above the electrode location, the upward travel of the hottest glass to and along the undersurface of the batch blanket, and the escape of the seed-forming gas bubbles through the thin batch layer as the hottest glass recirculates at and above. the electrode location, even though the molten glass is not "fined" in the conventional sense of holding it virtually stagnant for an extended period of time.
• the embodiment of Figure 3 differs from the embodiments of Figures 1 and 2 primarily in the improved conditioning to the desired forming temperature by means of a heat exchanger operative to cool the molten glass in the lower regions of the pool 101 and as it flows through the outlet aperture 105 and the bushing blocks 106 and 108.
• this heat exchange means is illustrated as a water jacket 120 which is of conventional design to provide a labyrinthian passage for a heat exchange medium, preferably cool water, which is circulated through the water jacket 120, the heat exchange fluid entering the water jacket through an inlet line 121 and exiting through an outlet 122.
• the water jacket 120 is inserted into and retained within an appropriately shaped recess 125 formed in a refractory bottom element 126, with the element 126 and the heat exchanger being held in place by a bottom support plate 127 and angle iron supports 128.
• This specific location and arrangement of the heat exchanger 120 is such that the flow of heat exchange fluid therethrough cools the furance bottom wall 104, the outlet passage 105, and the bushing blocks 106 and 108.
• the heat exchanger 120 in heat exchange re l at i on to t h e bottom o f t he f u rn a ce a n d t ne o u tl e t therefrom, heat is extracted from the molten glass in the bottom regions of the pool 101 and from that portion of the pool of glass 101 flowing through the bottom outlet and the bushing blocks interposed between the bottom outlet and the forming apparatus 110.
• FIG. 7 and 8 The cooling effect of the heat exchange means 120 is illustrated in Figures 7 and 8 wherein the rapid cooling of molten glass in the bushing well 105 and the bushing blocks 106 and 108 will be readily apparent.
• This same relatively rapid cooling is illustrated in Figure 8 of the drawings.
• the temperature profile of Figure 10 of the drawings illustrates both the rapid cooling of the glass and the fact that it is cooled in essentially isothermal planes, particularly in the bushing well and the bushing blocks, so that the glass entering the forming apparatus 110 is both (1) at a reduced temperature conducive to forming and (2) at a uniform temperature across substantially the entire body of glass flowing into the forming apparatus from the lower bushing block 108.
• an increase in the amount of cooling exerted by the heat exchanger 120 may result in an increased temperature differential across the body of glass flowing through the bushing blocks and entering the bushing without appreciably increasing the chilling of the center portion of the glass flowing therethrough.
• an increase in the flow of cool water through the heat exchanger 120 reduced the temperature at the center of the bushing block by less than -3.9°C (25o F) while reducing the temperature at the i n t e r f a c e of the bushing block and the molten glass by from about 23.9°C (75° F) to more than about 43.3°C (110° F).
• over-cooling by utilization of the heat exchanger 120 merely creates an increased temperature differential internally of the glass without materially reducing the overall temperature or the average temperature of the glass.
• the limiting capacity factor during operation of the furnace is the capability of the furnace to deliver glass to the forming apparatus 110 at a temperature at which it can be properly utilized in the forming apparatus. This temperature is substantially less than that generated at the hottest portions of the glass body 110, that is the temperature at the glass at and above the level of the electrodes.
• a greater quantity of glass can be melted ano cooled to the desired forming temperature.
• a furnace such as that illustrated in Figures 1 and 2 of the drawings can operate at a throughput of about 9.1 kilograms (20 pounds) or less per hour for a furnace which has an internal dimension of 457.2 mm by 762 mm (18" by 30").
• that version of the furnace illustrated in Figure 3 of the drawings and of the same internal dimensions can be operated at average throughputs on the order of 22.7 kilograms (50 pounos) per rour while maintaining essentially planar, isothermal flow without "channeling".
• the furnace 200 generally comprises side walls 201, end walls 202 and a bottom wall 203 of one type of refractory material and a lining for the respective walls and bottom consisting of a different type of refractory.
• the refractory of the walls 201, 202 and 203 a re of a conventional sintered zircon-type refractory.
• the walls, 200, 201 and 202 and the bottom 203 are lined with an erosion-resistant refractory which is essentially chromic oxide.
• Suitable refractories of this type a re manufactured by The Carborundum Company of Falconer, New York and sold under the tradename "Monofrax E” and by Corhart Refractories of Louisville, Kentucky under the tradename "C-1215 Chromic Oxide Refractory.”
• the lining for the walls and the bottom is indicated by reference numerals 205, 206 and 208, respectively.
• the refractory constituting the lining 205, 206 and 208 is of lower electrical resistivity at the operating temperature of the furnace 200 and the end walls 202 are cooled as by heat exchangers 210 ( Figure 5).
• the end walls only of the furnace of Figure 3 a re similarly lined and cooled.
• the composite side and Dottom walls confine a body of molten glass 207 heated by electrodes 209, as heretofore explained in connection with Figure 1.
• the lower wall 208 is provided with a centrally located outlet aperture or "bushing well" 212 which is also lined and which communicates with a plurality of stacked, centrally apertured bushing blocks 214, 216 and 218 which preferably a re of the same sintered zircon refractory as the walls 201, 202 and 203.
• a fiberglass forming bushing or other forming apparatus 220 Secured to the lowermost bushing block 218 is a fiberglass forming bushing or other forming apparatus 220.
• the bushing blocks 216 ana 218 a re provided with heat exchanger means indicated generally at 222 and specifically illustrated in Figure 6 of the drawings.
• the heat exchanger means 222 each comprises a tube 224 of platinum or heat-resistant material projecting through the side walls of the respective bushing block 216, 218 and having an enlarged medial portion 226 disposed within the bushing block 216 and projecting across the flow opening of the block 216. That portion 226 of the tube 224 internally of the bushing block is provided with an internal liner 228 of alumina or the like material to rigidify the tube portion 226.
• the alumina tube 228 has an interior passage 230 accommodating the flow of heat exchange fluid, such as air, introduced thereinto through the tube 224.
• the flow passage 230 and the tube 224 communicates with an air inlet line 232 through an air flow control valve mechanism 234 for accommodating the flow of air from the supply tube 232 through the tube 224 and the liner passage 230 to exit through an air outlet line 236 which is vented to an appropriate exhaust means.
• the intermediate bushing block 216 contains a pair of vertically spaced, laterally offset rows of heat exchangers 222, and the lower bushing block 218 contains a single row of such heat exchange elements 222. It will be appreciated that specific arrangements and constructions illustrated in Figures 4, 5 and 6 may be varied.
• the bottom 203 of the furnace is cooled by a heat exchanger 240 in flatwise contact therewith and receiving a coolant fluid, such as water, through an inlet 222 and discharging the coolant fluid through an outlet 244.
• a coolant fluid such as water
• a furnace as disclosed in Figure 3 was operated under the following conditions.
• a temperature profile was determined by measurements taken by thermocouples immersed manually through the batch layer to the indicated depth within the furnace as it was operating. Measurements were taken consecutively on the furnace centerline and at either end near the end wall.
• the feeding of particulate batch was interrupted during electrode insertion, temperature measurement and electrode removal. The interruption of batch feeding varied the batch thickness from normal which varied the heat loss upwardly through the batch layer as reflected in the temperature measurement at the top region of the furnace, at the 228.6 mm (9") level. Further, the temperature measured at the center! ine at the 0 level and at the next level were increased because the side wall locations were cooled by the refractory furnace bottom while the centerline location was not so cooled. The following readings were obtained:
• thermocouple measurements were taken along the centerline of the furnace at the indicated distance above the bushing.
• the technique of thermocouple measurements was as described in Example I.
• the bushing was operated at a set point of 1260-1288°C (2300-2350° F). The results obtained are plotted in the graph of
• the furnace was operated at a fixed throughput of 63E-04 K6/s (50 Ibs/hr), a melter maximum temperature of 1562°C (2843° F) and at bottom cooling of 22.7E-05 m3/s (3.6 gal/min). Thermocouple measurements were taken manually through the top of the furnace at the locations indicated in Figure 9 of the drawings.
• An electric furnace in accordance with this invention was hung in position beneath a batch feed system.
• Four electrodes were employed in the melter. They extended through side walls and were arranged as pairs of opposed, parallel electrodes. The electrodes were movable and could penetrate into the furnace until the tips of opposed electrodes are only 25 mm (one inch) apart.
• a production platinum bushing was installed below the melter with a refractory bushing block in place.
• the temperature of the molten material at the bushing will be at least 149°C (300° F) lower than the temperature of the molten material at the batch interface.
• This difference may, however, be as high as 343°C (650° F) depending upon the type of material being melted and furnace conditions. On occasion, the difference may be less than 149°C (300° F). However, this condition would not be encountered often.
• the bushing was a conventional textile bushing used to make continuous fibers. While E glass fibers and C glass fibers were produced, R glass or a basalt also could be made. Melter temperatures usually were above 1482oC (2700° F) and typically were about 1510°C (.2750° F). Bushing temperatures usually were above 1149°C (2100° F) and typically were about 1204°C (2200° F). Precautions of isolating the electrodes and grounding the power supply must be taken. Protecting the bushing and melter walls from short circuiting also must be provided. Otherwise, an electrolytic effect will be established between the grounded molybdenum electrodes, the platinum bushing grounded through the refractory and the molten glass.
• the anodic protection of forming means, such as bushings or feeders, for making glass fibers is accomplished by applying an anodic D.C. bias to a bushing which has been electrically grounded. This grounding can even occur through the refractory. While the anodic protection is described in terms of a grounded bushing, any portion of the melter, such as thermocouple or electrode made of precious metal, may be grounded in a similar manner. Also, there must be a cathodic material somewhere in the vicinity of the bushing to complete the D.C. circuit. The molybdenum electrodes of the melter often may serve the purpose of completing the D.C. circuit and acting as the cathode.
• the electrodes were spaced apart so that opposed tips were about 76.2 mm (3 inches) apart at the center of the furnace. During normal operation, the electrodes were backed out depending upon furnace conditions. Generally, opposing electrodes were about 101.6 to 127 mm (4 to 5 inches) apart during normal fiber forming conditions.
• the distance between electrodes also is dependent upon the refractory.
• the electrodes are spaced to minimize short-circuiting through the refractory.
• the electrodes are spaced so that the resistance between electrodes is less than the resistance between el ectrodes through refractory walls.
• One structure for doing this may be spaced apart opposed electrodes located within a vessel, wherein the electrodes consist of a first row of spaced apart electrodes and a second row of spaced apart electrodes, the second row being opposed to the first row and the electrodes from one row extending to terminate in spaced apart, generally aligned relationship with the electrodes extending from the other row.
• adjacent electrodes in a row have a lateral distance between them, wherein the electrodes at the end of each row have a lateral distance between them and the adjacent interior surface that is one-half the lateral distance between adjacent electrodes in that row.
• the distance between the electrodes and-the forming means also is important because there must be enough heat loss so that the forming means, e.g., a bushing, will operate.
• the heat loss can be easily adjusted with the electrodes of this invention to conform to the throughput of the furnace. In conventional unit melters with heater strips, only forming speeds or batch feeding could be adjusted in response to varying temperatures in the melter or forming means.
• the flow is merely downward beyond the heater strips.
• the spaced apart opposed electrode and controlled current flow of this invention heat by joule effect to provide molten material of uniform temperature to produce forming outlets located at the bottom of the melter.
• the spaced apart opposed electrodes and controlled current flow also establish an essentially isothermal condition across a given horizontal plane in the melter. These temperature gradients allow molten material to be formed directly from the melter without further processing.
• the above runs were carried out with a single bushing below the melter. Multiple bushings also may be utilized on a single melter.
• the electrodes may be inserted in the side walls of the forehearth thereby eliminating need for the large horizontal furnace and fining channel. This would eliminate any horizontal or lateral flow of molten material and provide a vertical flow of molten material to the forming means. Eliminating lateral flow prevents any interaction between bushings.
• One arrangement for carrying out this embodiment includes multiple openings in the floor for discharge of molten material therethrough with a forming means disposed at each opening to receive molten material discharged from the vessel.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Electrochemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Manufacturing & Machinery (AREA)
• Glass Melting And Manufacturing (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)
• Resistance Heating (AREA)
• Furnace Details (AREA)
• Vertical, Hearth, Or Arc Furnaces (AREA)

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• 1983
  • 1983-07-11 US US06/512,067 patent/US4528013A/en not_active Expired - Lifetime
  • 1983-07-22 IN IN918/CAL/83A patent/IN159076B/en unknown
  • 1983-07-26 DE DE8383902515T patent/DE3378630D1/de not_active Expired
  • 1983-07-26 JP JP58502615A patent/JPS59501357A/ja active Pending
  • 1983-07-26 HU HU833281A patent/HUT38287A/hu unknown
  • 1983-07-26 EP EP83902515A patent/EP0115509B1/en not_active Expired
  • 1983-07-26 AU AU18273/83A patent/AU562137B2/en not_active Ceased
  • 1983-07-26 WO PCT/US1983/001137 patent/WO1984000746A1/en active IP Right Grant
  • 1983-07-29 IT IT22358/83A patent/IT1163878B/it active
  • 1983-08-03 EG EG481/83A patent/EG16542A/xx active
  • 1983-08-03 ES ES524691A patent/ES524691A0/es active Granted
  • 1983-08-04 AR AR293809A patent/AR231960A1/es active
  • 1983-08-05 DD DD83253754A patent/DD216707A5/de unknown
  • 1983-08-05 CA CA000433990A patent/CA1207534A/en not_active Expired
• 1984
  • 1984-02-29 DK DK137084A patent/DK137084A/da not_active Application Discontinuation
  • 1984-03-30 FI FI841282A patent/FI841282A0/fi not_active Application Discontinuation
  • 1984-04-06 NO NO841378A patent/NO841378L/no unknown
  • 1984-08-14 ES ES535123A patent/ES8600726A1/es not_active Expired

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